Field of the Invention
The present invention relates to method for manufacturing module-type microfluidic paper chip using inkjet printing.
Background Art
Existing digital microfluidic chips are manufactured by performing complicated procedures, such as photolithography and etching, on a glass or silicon substrate (R. B. Fair, Microfluid Nanofluid, 3:245-281(2007)), and apparatuses and chemicals used herein are expensive and very harmful to the human body and environment. Most digital microfluidic chips are in closed systems (Robert J. Linhardt et al., J. AM. CHEM. SOC., 131:11041-11048(2009)), and have a disadvantage in that a cover plate needs to be removed in order to analyze products after several reactions on the chip. With respect to an open chip system (Abdelgawad, Park, and Wheeler J. Appl. Phys., 105:094506 (2009)), the existing methods are also employed in the forming process of electrode patterns during the manufacturing procedure thereof, and thus the above-described problems occur.
Through electrowetting, the movement of fluid can be controlled by electricity, and the electrowetting is employed in the digital microfluidic chips. In easy terms, the electrowetting phenomenon refers to the change of surface tension by electricity. This phenomenon was first discovered by Gabriel Lippmann (1845˜1921) in 1875. When acid water contained in the capillary tube, the concaved meniscus appears such that the height of center of water column is lower than the contact line between water and the inner wall of tube. The contact line which is slightly raised along the wall of tube is formed as a result of balance among the interfacial tensions of three phases, i.e., air, water and rigid wall, being in equilibrium state. When the electric potential applied water and the metallic tube the height water raised with the shape of meniscus changed with being less concaved, in other word the contact angle reduced as much as the applied capillary tension induced by electric potential.
Lippmann called it ‘electrocapillarity’, but no new light was shed on this technique for 100 years after that. Electrocapillarity occurred at a low voltage of only 1 V or smaller, and a voltage higher than 1 V decomposed water into oxygen and hydrogen. After that, electrowetting in which the surface tension can be controlled by a high voltage was discovered in 1990, just by introducing a thin insulating film between the acid water and the electrode. According to Bruno Berge, a metal plate was covered with a thin insulator, and then a drop of water was dropped thereon. When electricity was applied between the metal plate and the water droplet, the higher the voltage, the thinner the water drop spread. Through this manner, it was impossible to change the shape of a water drop even at a high voltage of several tens of V.
A carbon nanotube is a new material, in which hexagon shapes made of six carbon atoms are connected together in a tubular form, and which was discovered by Sumio Iijima at Research Institute of Nippon Electronic Company (NEC) in 1991 while analyzing a carbon mass that was formed on the cathode of graphite using the electric discharge method. As for the carbon nanotube, hexagon shapes made of six carbon atoms are connected together in a tubular form. The diameter of the tube is merely several to several tens of nanometers, and thus called as the carbon nanotube. One nanometer is 1/1,000,000,000 (one one-billion) meter, and 1/100,000 of one hair. The carbon nano tube has a similar electric conductivity to copper, the same thermal conductance diamond which is the most excellent in the natural system, and is 100 times stronger than the stainless steel. While the carbon fiber is broken by a variation of only 1%, the carbon nanotube can withstand a variation of even 15%. Since the carbon nanotubes were discovered, scientists have devoted themselves to searching a synthesis and application thereof, and thus have developed a lot of devices, such as a semiconductor, a flat display, a battery, an ultra-high strength fiber, a biosensor, and a TV monitor, using the carbon nanotubes.
Korean Patent Registration No. 10-0523765 provides a method for manufacturing a carbon nanotube array using supramolecular nano patterns. More specifically, disclosed is a method for manufacturing a carbon nanotube (CNT) array, the method comprising: forming an organic supramolecular thin film on a substrate; inducing a self-assembly of organic molecules through heat treatment; applying UV to the thus formed predetermined organic supramolecular structure to form a hole-shaped nano pattern; and arranging carbon nanotubes in the nano pattern. According to the above patent, in the manufacturing procedure of the CNT chip, the patterning is performed in a manner in which the self-assembly of organic supramolecules and the UV etching are used to form the pattern, and the CNTs are allowed to bind to the pattern or be arranged in the pattern. Therefore, the above patent has disadvantages in that the patterning process is complicated and the UV etching needs to be conducted, when compared with the present invention.
Korean Patent Application Publication No. 10-2011-0060028 provides a carbon nanotube-polymer complex and a method for directly patterning carbon nanotubes on a substrate in a particular direction using the same. More specifically, provided are a carbon nanotube-polymer complex and a method for directly patterning carbon nanotubes on a substrate in a particular direction using the same, in order to form patterns having orientation in a particular direction on a substrate including a carbon nanotube dispersion solution, a surfactant, and a polymer solution with viscosity. According to the above patent, for the adsorption of the carbon nanotube, the patterning is performed on the substrate by conducting treatment with a mixture solution of sulfuric acid/peroxide or UV/ozone treatment, and then removing a polymer portion from the carbon nanotube-polymer complex through separate chemical treatment. Therefore, the above patent has disadvantages in that the patterning process is complicated and the additional chemical process is needed, when compared with the patterning method of the present invention.
Due to the problems of the existing drop-based digital microfluidic chips, the development of digital microfluidic chip technology, based on a new mechanism of an open chip that can attain economical feasibility, simplify a complicated manufacturing process, and be applied to processes, such as several kinds of synthesis, is urgently needed. The present invention relates to an economical modular microfluidic chip manufactured by printing various shapes of patterns using a carbon nanotube ink, as a conductive ink, and employing inkjet printing and then cutting and assembling the patterns, and thus provides a modular type microfluidic chip with economical feasibility and high utilizability to solve the advantages.
Throughout the entire specification, many papers and patent documents are referenced and their citations are represented. The disclosures of cited papers and patent documents are entirely incorporated by reference into the present specification, and the level of the technical field within which the present invention falls and details of the present invention are explained more clearly.